A fire extinguisher, or simply an extinguisher, is a portable device that is used to extinguish small fires, generally in emergency situations. Fire extinguishers are a first line of defense against fires in many homes, offices, and other commercial buildings and can be easily operated when the need arises. In many situations, several fire extinguishers may be conspicuously located inside and/or outside of buildings within ready access by persons in an emergency. Some facilities provide fire extinguisher training to persons working in the facility and ensure that everyone knows the location of nearby fire extinguishers. A typical extinguisher includes a pressurized vessel, usually cylindrical, that contains a dischargeable agent to extinguish the fire.
Many countries have requirements related to the location and servicing of fire extinguishers. For example, in the United States, fire extinguishers are required in all buildings, except homes, and are required to be serviced and inspected by a fire protection service company at a particular frequency. Generally, fire extinguishers are inspected annually, internal maintenance is performed every 3 to 6 years, and hydrostatic testing is done every 5 to 12 years, depending on the type of extinguisher.
For both internal maintenance and hydrostatic testing, fire extinguishers are emptied of the agent and depressurized. The extinguisher is disassembled, inspected, cleaned, lubricated, and if necessary, hydrostatic testing is performed. Any extinguisher found defective is replaced. Otherwise, the extinguisher is refilled with agent and pressurized. In the case of dry agent (or dry chemical) fire extinguishers, the agent can be re-used if in good condition. The refilled extinguisher is tagged as having maintenance service and put back into service.
One system used for dry chemical fire extinguisher maintenance utilizes a generally funnel-shaped hopper. A high-pressure hose is attached to a ball valve on the side of the hopper, near its top. The top of the hopper is fitted with a perforated lid having a filter and an air inlet is located near the bottom of the hopper. The bottom of the hopper tapers to a discharge port that is sized to attach to a tube, which in turn is attached to a manifold. The manifold is a rubber stopper sized to fit the top of the fire extinguisher and has two ports. One port is attached to the tube and the other port is attached to a vacuum source.
In operation, the discharge nozzle of a fire extinguisher is attached to the free end of the high-pressure hose. The ball valve is opened and the fire extinguisher is discharged into the hopper. The perforated lid allows the pressurized gas to escape while retaining the dry chemical in the hopper. Once all the chemical is discharged, the fire extinguisher is removed for inspection and/or testing.
To refill, the manifold is attached to the top of the fire extinguisher. A vacuum source is started and as air is pulled through the hopper, the dry chemical is pulled into the fire extinguisher. The air inlet may be opened intermittently to “fluff” the chemical as needed and to assist the flow of the chemical from the hopper. Once the fire extinguisher is filled with the proper amount of dry chemical, the vacuum is removed and the fire extinguisher is pressurized.
This system has several drawbacks, however. Vacuum sources for refilling and gas sources for fluffing the dry chemical are large, heavy, and noisy. This means that fire extinguishers requiring service must be brought to a maintenance station, such as a facility or mobile vehicle, e.g., a van or truck that houses the maintenance system. A great deal of time is spent by the technician moving fire extinguishers from their installed location to the maintenance station and back to the installed location. To save time, some technicians may bring several fire extinguishers to the maintenance station and empty them into the refill system. However, the potential for cross-contamination of dry chemicals is greatly increased by doing so.
Additionally, because the dry chemical is discharged into the hopper at high pressure and velocity, the dry chemical can be pushed through the filter in the perforated lid into the atmosphere and can cause it to clog. Furthermore, the open discharge port at the bottom of the hopper can allow the dry chemical to be blown through the tube and attached manifold into the atmosphere, where it may be breathed by the technician.
During refill, dry chemical may become clogged due to being pulled by vacuum. In addition, dry chemical may also be pulled into the vacuum source, causing fouling and/or failure of the vacuum.